description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: /customtag.jsp(12,1) According to TLD or attribute directive in tag file, attribute value does not accept any expressions org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:39)

I found the problem, it was the taglib directive decleration: <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> The correct one should be: <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>